1. Field of the Invention
This invention relates to a process for producing novel hydrocarbon-soluble partially sulfonated polyol ester derivatives of a monoethylenically unsaturated C.sub.4 -C.sub.10 dicarboxylic acid material under conditions of reduced sediment formation as well as to the resulting substantially sediment-free product useful for preparing ashless dispersants utilized in lubricating oil and fuel compositions. In particular, this invention is directed to a sediment-free process involving the polyol esterification of alkenyl succinic anhydride to provide lubricating oil and fuel additives wherein said reaction is carried out in the presence of a sediment-reducing amount of an oil-soluble sulfonic acid or with an oil-soluble partially sulfonated polyol. The invention also relates to the sulfonated polyol ester and lubricating oil compositions thereof.
2. Description of the Prior Art
During the past several decades, ashless sludge dispersants have become increasingly important, primarily in improving the performance of lubricants in keeping the engine clean of deposits and permitting extended crankcase oil drain periods while avoiding the undesirable environmental impact of the earlier used metal-containing additives. Most commercial ashless dispersants fall into several general categories.
One category of ashless dispersants involves the esterification product of alkenyl substituted acids, e.g. polyisobutenyl succinic acids, with polyols, e.g. pentaerythritol, as taught in U.S. Pat. No. 3,381,022; however, the usual process of making such a dispersant requires not only an esterification catalyst (such as sulfuric acid, benzene sulfonic acid, p-toluene sulfonic acid, phosphoric acid, etc., see col. 5, lines 68-75) but must be carried out at such an elevated temperature that large amounts, i.e. in the range of 2 to 6 vol.%, of sediment are formed.
Sulfonic acids are also used in other esterification reactions such as: the condensation of polyisobutenyl succinic anhydride with a tetraalkylol urea (see U.S. Pat. No. 3,897,456); sulfonated styrene-divinylbenzene copolymer exchange resin for the esterification of an 8-300 carbon branched chain alkenyl succinic anhydride with a variety of alcohols (see U.S. Pat. No. 4,029,675); and, the reaction of a monocarboxylic acid with a polyol in the presence of methanesulfonic acid (see U.S. Pat. Nos. 4,029,675 and 4,025,447 corresponding to German DAS 2 520 459).
Sulfonate esters of polyols are known (see U.S. Pat. No. 2,703,808 for the reaction product of sulfonyl chlorides and pentaerythritol and U.S. Pat. No. 3,579,630 for disclosure of pentaerythritol tetrakis (p-toluene sulfonate)).
Finally, a fuel additive is reported in U.S. Pat. No. 4,059,414 as the reaction product of an alkyl benzene sulfonate and the derivative of a fatty acid and a trialkanolamine.